Prior to the present invention, magnet wheels have been used in conjunction with stators, for example, for monitoring the rotation of shafts, axles, and wheels. In particular, such equipment is useful to monitor vehicle wheels equipped with anti-locking devices. The stator consists, for instance, of a sensor which includes at least a permanent magnet and a coil. The segments of a magnet wheel, also known as a rotor which is connected to the rotating component, cross the electromagnetic field that is generated by the permanent magnet. As a result, the sequence of segments of ferromagnetic material and air gaps causes a change in the magnetic field which induces an alternating voltage in the coil.
The frequency of the alternating voltage generated in this manner is generally proportional to the angular velocity of the wheel. This characteristic allows the calculation of the number of revolutions of the rotating component. This is useful in the case of a wheel of a power vehicle, especially with the aid of the electronic system of an anti-lock device.
A magnet wheel of this kind, constructed in the shape of a disk the periphery of which has been cut to produce substantially evenly-sized air gaps in such a way that a row of teeth is created along the periphery, is known in the prior art.
For example, a magnet wheel of the kind mentioned above has been disclosed to the art from German Patent DE-OS 29 39 643. The magnet wheel taught in this reference consists of a disk-shaped, solid ferromagnetic material which at its periphery has a series of segments oriented in the direction of rotation and consisting each of a tooth and an adjoining, about equally sized air gap. It is known that the manufacture of magnet wheels of this kind is very complex and costly. Such high cost is because the manufacture of such magnet wheels usually requires several operations of chip removing. In addition, the weight of a magnet wheel of this kind, manufactured from ferromagnetic material, makes complex mounting devices necessary to hold the rotor in place. These mounting devices are subject to extremely varied forces particularly when applied in utility vehicles. The construction of the mounting devices is very complex, particularly because even slight spatial deviations between sensor and magnet wheel can cause significant disturbances in signal transmission. These disturbances may lead to faulty brake control in the vehicle wheel concerned. Obviously, this condition is highly undesirable.
Furthermore, magnet wheels of this kind cannot be manufactured in large numbers at an economical price. The reason for such high cost is that almost every vehicle type requires a special method of fastening. Further adding to the cost is the added storage requirement. This is particularly true for retrofitting anti-lock-protected brake systems.